Clamp mountings of this type are already known and comprise a one-piece cross member including a plurality of suspension clamps. In profile each clamp is shaped like a horseshoe. The ends of the arms of the horseshoe have inwardly directed rims intended for retaining the rail. The cross member is fixed to any convenient fixed structure, and specific examples of this kind of embodiment are to be found in published German patent specification No. 2 453 754.
This clamp mounting constitutes the closest prior art to the invention in that it comprises a cross member which is perpendicular to the rail direction and which supports a plurality of clamps or rail-fixing members.
In addition, other mountings are commonly used which do not include a cross member and in which single clamps are directly fixed to a fixed structure by screw means constituted by a threaded rod and a nut.
Some such single clamps are made from one piece of metal or plastic; others are made from two or three parts which are assembled by screws or bolts, as described in published French patent specification No. 2 185 838.
Finally, it should be observed that a clamp may be used to fix not just a single rail, but also a plurality of rails inserted in a single sheath.
All the clamp assemblies described above suffer from various drawbacks.
A first drawback relates to the fixing of the clamp assembly to the fixed structure. In the prior art, as mentioned above, such fixing is constituted by a threaded rod co-operating with a nut.
In a mounting which includes a single clamp, it will readily be understood that there must be as many fixing points as there are clamps. The time taken to mount the clamps is thus rather long. Additionally, the screw means used for fixing are generally made of stainless steel and are thus rather expensive. Further, other drawbacks result from the difficulty of accurately placing fixing holes in a fixed structure. As a result the rails are not completely parallel.
Finally, known clamp mountings are difficult to properly align with the rail direction since they tend to pivot about the axis of the fixing rod. This results in a twisting phenomenon which causes stress to be applied to the power supply rails.
Another drawback of the prior art concerns the placing and locking of the rails themselves in the suspension clamps.
Some clamps, as explained above, need to be opened in order to insert the rail and then closed by means of screws or bolts. In such cases, it takes a long time to install a rail because of a very large number of screws that need to be tightened.
When the rails are inserted in clamps having resilient arms, it is true that less time is required to install the rails, however the rails are not held in a secure manner. That is why this method of fixing can only be used with lightweight rails.
In other cases, the clamps are fitted over an end of the rail and must then be slid along the length thereof, i.e. several meters, up to their mounting positions; such assembly takes a long time.
Preferred embodiments of the present invention remedy these various drawbacks and propose a clamp mounting assembly which may be rapidly fixed to a fixed structure, and whose angular orientation may be easily and acurately adjusted; in addition, the fixing cost is not very great, and the power supply rails are rapidly installed and are retained in a secure manner.